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July 2008

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Subject:
From:
Brian Ellis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Brian Ellis <[log in to unmask]>
Date:
Fri, 25 Jul 2008 19:12:00 +0300
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1. with a good water wash, just th same as when you solder the beastie 
with a WS flux. No messing, no short cuts.

2. categorically NO! Alcohol may not dissolve the residues, either
organic or metallic

3. Yes! This is why you need to give it a full-scale wash. You cannot
clean with a brush: all you will do is harm by spreading those ionics
all over the place.

WS=WATER soluble - un point, c'est tout!

Brian

Jean-François Bissonnette wrote:
> Hello Technetters,
>
>
>
> We experienced some problems after reworking circuit boards, I would like to have inputs on the following.
>
>
>
> The problem found is capacitor leakage. The capacitor was added manually after automated production. The boards were coated with acrylic conformal coating.
>
>
>
> 1- How should a WS flux be cleaned after a rework?
>
> 2- Can WS be cleaned with alcohol? If not what would happen?
>
> 3- When reworking a SMT component, can WS flux be trapped under the component and cause leakage. The rework was cleaned with a brush or similar method.
>
>
>
> We think that the rework method was as follow (to fix a possible contamination under the component)
>
> a- SMT component is removed (possibly directly through the conformal coating)
>
> b- Using coating thinner, the area is cleaned and verified under UV to ensure no coating is present.
>
> c- WS flux is added
>
> d- Component is soldered back in place
>
> e- Area is cleaned with isopropyl alcohol
>
> f- Coating is added
>
>
>
> I think I've read that cleaning WS flux with alcohol is a NO NO! Can anyone confirm and comment?
>
>
>
> Jean-Francois
>
>
>
>
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